A seamless Super Duplex UNS S32550 tube is a high-strength tubing component made from the Ferralium 255 alloy without weld seams. This tube primarily consists of approximately 25% chromium with balanced nickel, molybdenum, copper, and nitrogen additions. It is one of the grades of super duplex tubes that provide higher yield strength than 316L and is used in offshore and chemical sectors due to its resistance to seawater.
ASTM A789 Super Duplex Steel UNS S32550 Seamless Tubes Manufacturer
We at Zhejiang Xintongda Special Steel (XTD) are a trusted manufacturer in China and a supplier of Super Duplex Steel UNS S32550 seamless tubes, best known as Ferralium 255 or SDSS. The material comprises a dual-phase microstructure containing approximately 25% chromium, 4.5–6.5% nickel, 3% molybdenum, 1.5-2.5% copper, and 0.2% nitrogen to improve pitting and crevice corrosion resistance. We manufacture these tubes as per the ASTM A789 standards. This unique product is better than austenitic alloys like 304 and 316 in providing superior strength (yield of roughly 550 MPa) and outstanding resistance to acids and chlorides. Our tubes are ideal for demanding offshore, chemical, and desalination systems. As an international ISO-certified company, we maintain a supply capacity of 25,000 tons annually. We ensure delivery in a lead time of around 1 week for stock products and 15-60 days for production orders to support global project requirements.
Product specifications cover:
-
Standard ASTM A789 -
OD Range 6-720mm -
Thickness 1 to 65 mm -
Length ≤ 22 m
Get a free quote now
Technical Data
Technical Data
Manufacturing Process of Super Duplex S32550 Seamless Tubes
We begin the process by heating a solid billet and forming it into a high-quality hollow shell through high-temperature piercing. Then it is followed by precision cold drawing and rolling. Each tube is solution annealed and water quenched to achieve a balance of austenite and ferrite. For the detailed manufacturing process, please refer to our manufacturing process page.
Key features of ASTM A789 UNS S32550 Tubes
Super Duplex UNS S32550 tubes offer 6 primary features that can withstand high-stress industrial environments. The key features are mentioned below:
- Resistance to Pitting and Crevice Corrosion: The high chromium and molybdenum content provides a PREN value of approximately 38–40 to prevent localised metal loss. This feature ensures that the tube can withstand seawater and harsh chemical compositions without surface damage.
- Resistance to Stress Corrosion Cracking: The mixed duplex structure prevents cracks from causing sudden structural failure in chloride-rich areas. This unique property allows our tubes to operate safely in high-temperature brine and offshore applications.
- Low Thermal Expansion: S32550 alloy provides a lower coefficient of thermal expansion than standard austenitic steels, which reduces stress during temperature fluctuations. This feature reduces thermal stress during temperature fluctuations, making these tubes ideal for high-temperature cycling conditions.
- Toughness and Ductility: Our tubes maintain a high yield strength of around 550 MPa with excellent elongation at sub-zero temperatures to ensure safety in diverse climates. This mechanical toughness prevents brittle fractures, even when the material is subject to high mechanical loads.
- Erosion and Abrasion Resistance: It enhances hardness compared to conventional austenitic grades that resist wear from fast-moving fluids containing sand or other abrasive particles. This makes the product a preferred choice for slurries in the mining and paper industries.
- Resistance to Non-Oxidising Acids: The addition of copper enhances the ability of the material to withstand corrosion in non-oxidising acids like sulphuric acid. This feature provides a wider safety margin in chemical plants compared to other super duplex grades.
Equivalent grades of Super Duplex Steel S32550 tubes
UNS S32550 is the main equivalent designation for Ferralium 255, a grade widely recognised for superior copper-enhanced corrosion resistance. The table below helps engineers find the right material for industrial applications.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| Super Duplex Steel 32550 | S32550 | — | — | — | X2CrNiMoN25-6-3 | 1.4507 | — |
100% Certified Testing & Documentation
- EN 10204 3.1 and EN 10204 3.2 Material Test Certificates (MTC)
- Raw Materials Certificate
- 100% PMI
- Heat Treatment Charts
- Third-Party Inspection Report
- Surface roughness and size measurement
- Manufacturer Test Certificate (Impact Testing, Flattening, Flare, Bend, Hardness, Intergranular, Pitting Corrosion, Grain size, ET, UT, HT)
- Laboratory Test Certificate from the Government-Approved Lab
Where are Super Duplex S32550 tubes used?
S32550 super duplex stainless steel seamless (SMLS) tube is used in 5 industrial applications where extreme durability and chemical stability are required. The following industries require S32550 tubes:
Chemical Processing
Processing plants install S32550 super duplex stainless steel seamless tubes in reactors and heat exchangers to manage hot phosphoric and sulphuric acids. The copper content prevents the metal from dissolving in these aggressive acidic environments.
Seawater Desalination Plants
Desalination plants use S32550 tubes in high-pressure systems that use reverse osmosis to prevent pitting from concentrated brine. The material ensures that the filtration units operate for a long time without requiring frequent tube replacements.
Marine Engineering
Our tubes are used in propeller shafts, rudders and subsea equipment exposed to constant saltwater contact. The high fatigue strength of the alloy prevents mechanical failure under continuous wave motion.
Paper Industry
In the pulp and paper industry, UNS S32550 (Ferralium 255) super duplex seamless tubes are used in demanding applications where high strength and strong resistance to corrosive chemicals and elevated temperatures are required.
Oil and Gas Industry
The oil and gas industry handles sour gas using seamless super duplex tubes in downhole equipment and subsea pipelines. It prevents stress corrosion cracking by ensuring safety in high-pressure offshore wells.
Frequently Asked Questions
-
What is a seamless Super Duplex UNS S32550 tube?
-
What is the difference between S32550 tubes and S32750/S32760 tubes?The difference between the S32550 tube and the S32750/S32760 tube is mainly because of the copper content. The S32550 contains 1.5% and 2.5% copper for better acid resistance. While all three are super duplex grades, S32550 is often preferred for specific sulphuric acid applications where S32750 tubes might not perform that well.